Communication device, communication method, communication computer program product, and communication system

ABSTRACT

An electronic apparatus includes processing circuitry functioning as an acquisition part and a change part, and includes communication circuitry. The acquisition part acquires a control command regarding the volume of traffic per unit time. The change part changes a communication parameter to reduce the volume of traffic per unit time in accordance with the control command. The communication circuitry performs multi-hop wireless communications with the volume of traffic according to the changed communication parameter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2019-000705, filed on Jan. 7, 2019; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a communication device(an electronic apparatus), a communication method, a communicationcomputer program product, and a communication system.

BACKGROUND

A technique is disclosed for preventing data congestion in a system thatperforms wireless communications of communication data such as videodata. For example, a technique is disclosed for recovering a burst lossby a specified time by transmitting an error correcting packet laterthan video data by the specified time. Conventional technologies aredescribed in Japanese Patent Application Laid-open No. 2013-70418, forexample.

Conventional technologies, however, have had difficulty in preventingcongestion of communication data communicated over a multi-hop network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a communication system according to anembodiment;

FIG. 2 is a hardware configuration diagram of a communication device;

FIG. 3 is a functional block diagram of the communication device;

FIG. 4 is a schematic diagram illustrating a data formation ofcommunication history information;

FIG. 5 is a schematic diagram illustrating a data formation ofconnection management information; and

FIG. 6 is a flow chart illustrating a flow of communication processing.

DETAILED DESCRIPTION

A communication device (an electronic apparatus) includes processingcircuitry functioning as an acquisition part and a change part, andincludes communication circuitry. The acquisition part acquires acontrol command regarding the volume of traffic per unit time. Thechange part changes a communication parameter to reduce the volume oftraffic per unit time in accordance with the control command. Thecommunication circuitry performs multi-hop wireless communications withthe volume of traffic according to the changed communication parameter.

The communication device (electronic apparatus), the communicationmethod, the communication computer program product, and a communicationsystem are described in detail below with reference to the accompanyingdrawings.

FIG. 1 is a schematic diagram illustrating an example of a communicationsystem 1 according to the present embodiment.

The communication system 1 includes an aggregation device 12 and aplurality of communication devices (electronic apparatuses) 10. Thenumber of communication devices 10 may be any number. FIG. 1 illustrates9 communication devices 10 (a communication device 10B to acommunication device 10J), as an example. The aggregation device 12 andthe communication devices 10 constitute a multi-hop network on which theaggregation device 12 serves as a root node.

The aggregation device 12 is a parent node to all of the communicationdevices 10 included in the communication system 1 and is sometimesreferred to as a root node. In the communication system 1 of the presentembodiment, a form is described in which the communication devices 10are connected wirelessly to the aggregation device 12 in a treestructure. The structure of the communication system 1 is not limited toa tree structure.

The communication devices 10 are nodes that constitute a multi-hopnetwork. The communication devices 10 perform wireless communications byrelaying communication data (transmission data) via multi-hop wirelesscommunications. In a multi-hop wireless communication, a communicationfrom a source communication device 10 to a destination communicationdevice 10 (or the aggregation device 12) is performed by being relayedby other communication devices 10. Thus, communication data transmittedby each of the communication devices 10 is transmitted to theaggregation device 12 by being relayed by other communication devices 10or directly. The aggregation device 12 aggregates the communication datatransmitted by each of the communication devices 10.

A publicly known communication method may be used for multi-hop wirelesscommunications performed by the communication devices 10 and theaggregation device 12. For example, the communication devices 10 and theaggregation device 12 perform multi-hop wireless communications using apublicly known time division wireless communication system.

FIG. 1 illustrates an example of communications from each of thecommunication devices 10 to the aggregation device 12 in the upstreamdirection. The arrows in FIG. 1 indicate directions of transmittingcommunication data. In the communication system 1, however,communications are also performed from the aggregation device 12 to eachof the communication devices 10 in the downstream direction.

A hardware configuration of the communication devices 10 is describednext.

FIG. 2 is an example of a hardware configuration diagram of thecommunication devices 10.

The communication devices 10 each has a central processing unit (CPU)13A, a read only memory (ROM) 13B, a random access memory (RAM) 13C, anI/F part 13D, or the like connected to one another via a bus 13E, andhas a hardware configuration that uses a normal computer.

The CPU 13A is an arithmetic unit that controls the communicationdevices 10. The ROM 13B stores therein computer programs that enable theCPU 13A to execute various types of processing, for example. The RAM 13Cstores therein data necessary for various types of processing executedby the CPU 13A. The I/F part 13D is an interface through which toconnect to an external device or any other device.

Computer programs executed in the communication devices 10 of thepresent embodiment are provided by being preinstalled on the ROM 13B orthe like. The computer programs executed in the communication devices 10of the present embodiment may be configured to be provided by beingrecorded into a computer-readable recording medium, such as a CD-ROM, aflexible disk (FD), a CD-R, a digital versatile disc (DVD), in a fileformat installable on the communication devices 10 or an executable fileformat.

A functional configuration of the communication devices 10 is describednext.

FIG. 3 is a functional block diagram illustrating a functionalconfiguration of the communication devices 10. FIG. 3 illustrates afunctional block diagram of the communication device 10C as an example.However, any communication devices 10 (the communication device 10B tothe communication device 10J) other than the communication device 10Cmay have the same configuration as that of the communication device 10C.

The communication device 10 has a control unit 14, a communication unit16, and a storage unit 18. The control unit 14, the communication unit16, and the storage unit 18 are connected to one another so as to becapable of giving and receiving data or signals.

The communication unit 16 is a communication function unit that performsmulti-hop wireless communications with other communication devices 10.The communication unit 16 may be implemented by using a publicly knownwireless function of performing multi-hop wireless communications. Thecommunication unit 16 performs multi-hop wireless communications ofcommunication data with other communication devices 10 under the controlof the control unit 14.

The communication data is data communicated over a multi-hop network.For example, the communication data includes one or more frames andforward error correction (FEC) codes. The communication data may be in aform that includes no FEC.

The storage unit 18 stores therein various types of data. The storageunit 18 is, for example, a RAM, a semiconductor memory device such as aflash memory, a hard disk, an optical disk, a memory card such as an SDcard, and a universal serial bus (USB) memory. The storage unit 18 maybe a storage device disposed outside the communication device 10. Thestorage unit 18 may also be a storage medium. Specifically, the storagemedium may store or temporarily store therein computer programs orvarious types of information after being downloaded over a local areanetwork (LAN) and the Internet. The storage unit 18 may also be made upof a plurality of storage media.

In the present embodiment, the storage unit 18 stores therein acommunication parameter 18A, communication history information 18B, andconnection management information 18C. The details of such informationwill be described later.

The control unit 14 includes communication circuitry (a communicationcontrol part 14A) and processing circuitry (a detection part 14B, adetermination part 14C, a generation part 14D, an acquisition part 14E,and a change part 14F).

These parts are each implemented, for example, by one or moreprocessors. For example, the aforementioned parts may be implemented bycausing a processor such as a CPU to execute a computer program, inother words, via software. The aforementioned parts may be implementedvia a processor such as an integrated circuit (IC), in other words, viahardware. The aforementioned parts may be implemented by making combineduse of software and hardware. In a case in which a plurality ofprocessors is used, each processor may implement one of theaforementioned parts, or may implement two or more of the aforementionedparts.

A processor reads and executes a computer program saved in the storageunit 18, thereby implementing the aforementioned parts. Instead ofsaving a computer program in the storage unit 18, the computer programmay be directly built in a circuit of the processor. In this case, theprocessor reads and executes the computer program built in the circuit,thereby implementing the aforementioned parts.

The communication control part 14A controls the communication controlpart 14A so as to perform multi-hop wireless communications ofcommunication data with the volume of traffic according to thecommunication parameter 18A.

The communication control part 14A reads the communication parameter 18Afrom the storage unit 18. The communication parameter 18A is stored inadvance in the storage unit 18 and is changed by the change part 14F tobe described later.

The communication parameter 18A is a parameter for the volume of trafficper unit time. Specifically, the communication parameter 18A includes atleast one of a bit rate of communication data and a frame rate of thecommunication data.

The communication control part 14A controls the communication controlpart 14A so as to perform multi-hop wireless communications ofcommunication data to be communicated at a bit rate and a frame rateindicated in the communication parameter 18A.

The communication parameter 18A may further include a FEC parameter.

The FEC parameter is, for example, redundancy of data.

In a case in which the communication parameter 18A includes a FECparameter, the communication control part 14A may execute processing forgenerating error correction data for communication data to becommunicated in accordance with the FEC parameter, and perform multi-hopwireless communications.

The communication control part 14A updates the communication historyinformation 18B every time communication data to be transmitted istransmitted to other communication devices 10 by performing a multi-hopwireless communication.

FIG. 4 is a schematic diagram illustrating an example of a dataformation of the communication history information 18B. Thecommunication history information 18B is information in which acommunication date and time, a node ID of a communication destination,and a communication result are correlated.

The communication date and time represent a date and time whencommunication data is transmitted to another communication device 10.The communication date and time may be any information that indicatestiming and is not limited to a date and time.

The node ID of a communication destination is identification informationthat identifies the communication device 10 or the aggregation device 12to which communication data is communicated. In the present embodiment,the node ID of a communication destination is indicative of anothercommunication device 10 or the aggregation device 12 that serves as aparent node and is adjacent to the communication device 10 from whichthe communication data is communicated, alternatively is indicative ofanother communication device 10 that serves as a child node and isadjacent to the communication device 10 from which the communicationdata is communicated.

The parent node refers to another communication device 10 with which thecommunication device 10 performs multi-hop wireless communications, andthat is on the higher side and closer to the aggregation device 12.Being “closer to the aggregation device 12” means that the number ofhops to reach the aggregation device 12 is smaller than thecommunication device 10 from which the communication data iscommunicated. The child node refers to another communication device 10with which the communication device 10 performs multi-hop wirelesscommunications, and that is on the lower side and farther from theaggregation device 12. Being “farther from the aggregation device 12”means that the number of hops to reach the aggregation device 12 islarger than the communication device 10 from which the communicationdata is communicated.

The node ID of a communication destination only needs to beidentification information that is capable of identifying thecommunication device 10 or the aggregation device 12 to which thecommunication data is communicated. For example, the node ID of acommunication destination is an Internet protocol version 6 (IPv6)address, a media access control (MAC) address, an IPv4 address, and ahost name of a domain name system (DNS), but not limited thereto.

The communication result is information indicating success or an errorin the communication.

In a case in which a multi-hop wireless communication of communicationdata is performed and the communication is successful, the communicationcontrol part 14A correlates with one another the communication date andtime, the node ID of the communication destination of the communicationdata, the communication result indicating success in the communication,and enters the correlated information in the communication historyinformation 18B. Meanwhile, in a case in which the communication isjudged to have an error, the communication control part 14A correlateswith one another the communication date and time, the node ID of thecommunication destination of the communication data, the communicationresult indicating an error in the communication, and enters thecorrelated information in the communication history information 18B.

The communication control part 14A determines whether at least a part ofpackets included in communication data is lost while a multi-hopwireless communication of the communication data is being performed withanother communication device 10. The communication control part 14A maydetermine a packet loss by a publicly known method. When thecommunication control part 14A has determined that a packet was lostwhile a multi-hop wireless communication of the communication data isbeing performed, the communication control part 14A may determine thecommunication to have an error. When the communication control part 14Ahas determined that no packet was lost while a multi-hop wirelesscommunication of the communication data is being performed, thecommunication control part 14A may determine that the communication issuccessful.

The communication control part 14A then notifies the detection part 14Bof a communication result indicating success or an error in thecommunication.

The detection part 14B detects a packet loss of communication data to betransmitted. A packet loss refers to at least a part of one or morepackets included in communication data being lost. The detection part14B detects a packet loss when receiving a communication resultindicating a communication error from the communication control part14A.

The determination part 14C determines occurrence of a burst loss of thecommunication data when the detection part 14B has detected a packetloss.

A burst loss refers to a loss of one or more packets included incommunication data occurring suddenly with a volume equal to or morethan a threshold value per unit time. The threshold value may be preset.

For example, the determination part 14C determines that a burst loss hasoccurred when the communication history information 18B satisfies apredetermined condition. A predetermined condition is, for example, acase in which communication errors are entered in the communicationhistory information 18B for a predetermined number of times in a row.The predetermined number of times may be preset. The predeterminednumber of times is, for example, ten times. A predetermined condition isalso, for example, a case in which a predetermined number ofcommunication results in a row from the present toward the past isindicative of communication errors at a ratio equal to or higher than apredetermined ratio. The predetermined number of times and thepredetermined ratio may be preset. The predetermined number of times is,for example, 30 times, but is not limited to this value. Thepredetermined ratio is, for example, 80%, but is not limited to thisvalue.

In a case in which an error correction using FEC is unable to be made tocommunication data that has previously been determined to have acommunication error, the determination part 14C may determine that thecase has a burst loss. The determination part 14C can use a publiclyknown method to determine whether error correction is able to be made tocommunication data by using FEC.

In a case in which at least one of the following is satisfied: thecommunication history information 18B satisfies a predeterminedcondition; and an error correction using FEC is unable to be made tocommunication data, the determination part 14C may determine occurrenceof a burst loss.

The generation part 14D generates a control command signal (controlcommand) when a burst loss is determined to have occurred.

The control command signal is a signal regarding the volume of trafficper unit time.

For example, the control command signal is a command signal. The commandsignal is a signal to instruct the volume of traffic per unit time, whenmulti-hop wireless communications are performed, be changed so as to besmaller than the current volume.

The control command signal may also be a definition signal predefinedwith a receiving end of the control command signal.

Assume that a control command signal is the aforementioned commandsignal or the aforementioned definition signal. In this case, thereceiving end of the control command signal may, when having determinedthat received data is the control command signal representing theaforementioned definition signal or the aforementioned command signal,change the volume of traffic per unit time so as to be smaller than thecurrent volume.

For example, the control command signal may also be a signal indicatinga value of the communication parameter after being changed. The value ofthe communication parameter after being changed may be a value obtainedby reducing the volume of traffic per unit time when multi-hop wirelesscommunications are performed to be smaller than the current volume.

The generation part 14D then notifies the communication control part 14Aof a generated communication control signal.

The generation part 14D refers to the connection management information18C and identifies a node ID of a communication destination to which thecommunication control signal is transmitted. The generation part 14Dthen notifies the communication control part 14A of the communicationcontrol signal and the node ID of the communication destination.

The connection management information 18C is information that specifiesa parent node ID of each of the communication devices 10 included in thecommunication system 1.

FIG. 5 is a schematic diagram illustrating an example of a dataformation of the connection management information 18C. The connectionmanagement information 18C is information in which a node ID and anadjacent parent node ID are correlated. The node ID is identificationinformation about each of the communication devices 10 included in thecommunication system 1. The adjacent parent node ID is identificationinformation about another communication device 10 that performsmulti-hop wireless communications with the communication device 10identified by the corresponding node ID, and that is a parent nodeadjacent to the relevant communication device 10 on the aggregationdevice 12 side.

The connection management information 18C is generated by theaggregation device 12 when a network topology of the multi-hop networkis constructed, for example. The aggregation device 12 generates theconnection management information 18C by a publicly known method on thebasis of the information aggregated from the communication devices 10.The aggregation device 12 then delivers the connection managementinformation 18C to each of the communication devices 10 included in thecommunication system 1 by performing multi-hop wireless communications.Thus, the connection management information 18C is stored in each of thecommunication devices 10 included in the communication system 1. In acase in which the network topology is changed, the aggregation device 12may deliver the connection management information 18C after beingchanged to the communication devices 10 by a publicly known method.Thus, the latest connection management information 18C is to be storedin each of the communication devices 10 included in the communicationsystem 1. When a network topology is constructed, each of thecommunication devices 10 may generate the connection managementinformation 18C. In this case, the connection management information 18Cmay be information indicating the connection relation of thecommunication system 1 in part, instead of the communication system 1 inwhole.

Return to FIG. 3, and the description is continued. The generation part14D reads, from the connection management information 18C, the adjacentparent node ID corresponding to the node ID of the communication device10 into which the generation part 14D is incorporated. The generationpart 14D also reads, from the connection management information 18C, theadjacent parent node ID corresponding to the node ID indicating the readadjacent parent node ID in sequence. In this manner, the generation part14D reads identification information (adjacent parent node ID) about oneor more of the other communication devices 10 that are connected in thedirection toward the communication destination of the communication datafor which a packet loss is detected, over the communication path ofmulti-hop wireless communications.

The generation part 14D notifies the communication control part 14A ofthe read identification information and the generated control commandsignal.

The communication control part 14A receives the control command signalfrom the generation part 14D. The communication control part 14A outputsthe control command signal to the acquisition part 14E. Thecommunication control part 14A also controls the communication unit 16so as to communicate the control command signal to each of one or moreof the communication devices 10 identified by the identificationinformation received from the generation part 14D by performingmulti-hop wireless communications.

Thus, the communication control part 14A is capable of controlling thecommunication unit 16 so as to transmit the control command signalgenerated by the generation part 14D to one or more of the othercommunication devices 10 that are connected in the direction toward thecommunication destination of the communication data for which a packetloss is detected, over the communication path of multi-hop wirelesscommunications. At this time, the communication control part 14A mayperform multi-hop wireless communications with the volume of trafficaccording to the communication parameter 18A stored in the storage unit18.

As described above, the communication devices 10 included in thecommunication system 1 have the same configuration as one another. Thus,the communication device 10 receives, from another communication device10, a control command signal generated in another communication device10 by performing multi-hop wireless communications in some cases.

In this case, the communication control part 14A outputs, to theacquisition part 14E, the control command signal received by thecommunication unit 16 from another communication device 10.

The acquisition part 14E acquires the control command signal. Theacquisition part 14E acquires, through the communication control part14A, the control command signal generated by the generation part 14D.The acquisition part 14E also acquires, through the communication unit16 and the communication control part 14A, the control command signalgenerated by the generation part 14D in another communication device 10.

The acquisition part 14E outputs the acquired control command signal tothe change part 14F.

The change part 14F changes the communication parameter 18A to reducethe volume of traffic per unit time in accordance with the controlcommand signal.

Specifically, the change part 14F decreases at least one of the bit rateand the frame rate indicated in the communication parameter 18A. Forexample, the change part 14F changes the bit rate so as to be a valuesmaller than the value of the current bit rate. For example, the changepart 14F changes the frame rate so as to be a value smaller than thevalue of the current frame rate.

Through the processing, the change part 14F changes the communicationparameter 18A to reduce the volume of traffic per unit time of thecommunication data transmitted from the communication unit 16 byperforming multi-hop wireless communications.

The communication control part 14A transmits the communication data toother communication devices 10 with the volume of traffic according tothe changed communication parameter 18A by performing multi-hop wirelesscommunications. Thus, the volume of traffic of the communication datacommunicated from the communication unit 16 to other communicationdevices 10 is reduced under the control of the communication controlpart 14A.

As described above, the communication parameter 18A may further includea FEC parameter. In this case, the change part 14F changes the FECparameter to reduce the communication data in accordance with thecontrol command signal. Specifically, the change part 14F changes theFEC parameter to reduce the redundancy of data, which is a FECparameter.

Changing the FEC parameter can reduce data transmitted over themulti-hop wireless network, thereby reducing congestion.

The change part 14F may change the communication parameter 18A stored inthe storage unit 18 to a preset initial value when the power of thecommunication device 10 is turned on after having been turned off.

An example is described next of a flow of communication processingexecuted by the communication device 10 of the present embodiment.

FIG. 6 is a flow chart illustrating an example of a flow ofcommunication processing executed by the communication device 10.

The communication control part 14A first determines whether to transmitcommunication data to another communication device 10 by performing amulti-hop wireless communication (Step S100). For example, whenreceiving communication data from another communication device 10, thecommunication control part 14A determines to transmit the communicationdata to another communication device 10. For example, the communicationcontrol part 14A determines to transmit the predetermined communicationdata to another communication device 10 when a predetermined timing hasbeen reached.

If the determination is affirmative at Step S100 (Yes at Step S100), theroutine continues to Step S102. At Step S102, the communication controlpart 14A reads the communication parameter 18A from the storage unit 18(Step S102). The communication control part 14A then controls thecommunication control part 14A so as to perform a multi-hop wirelesscommunication of the communication data to be communicated, inaccordance with the communication parameter 18A read at Step S102. Thiscontrol causes the communication unit 16 to transmit the communicationdata (Step S104).

Subsequently, the communication control part 14A determines whether thecommunication is successful for the transmission of the communicationdata at Step S104 (Step S106). The communication control part 14A makesthe determination at Step S106 by judging whether at least a part ofpackets included in the communication data is lost while a multi-hopwireless communication of the communication data is being performed withanother communication device 10.

If the determination is affirmative at Step S106 (Yes at Step S106), theroutine continues to Step S108. At Step S108, the communication controlpart 14A updates the communication history information 18B (Step S108).At Step S108, the communication control part 14A correlates with oneanother the communication date and time, the node ID of thecommunication destination, the communication result indicating successin the communication, and enters the correlated information in thecommunication history information 18B. This routine is then ended.

Meanwhile, if the determination is negative at Step S106 (No at StepS106), the communication control part 14A updates the communicationhistory information 18B (Step S110). At Step S110, the communicationcontrol part 14A correlates with one another the communication date andtime, the node ID of the communication destination, the communicationresult indicating the error in the communication, and enters thecorrelated information in the communication history information 18B.

Subsequently, the communication control part 14A outputs thecommunication result indicating the error in the communication to thedetection part 14B. The detection part 14B detects a packet loss byreceiving the communication result indicating the error in thecommunication (Step S112).

Subsequently, the determination part 14C determines whether a burst losshas occurred (Step S114). The determination part 14C makes thedetermination at Step S114 by judging whether the communication historyinformation 18B satisfies a predetermined condition. In a case in whichat least one of the following is satisfied: the communication historyinformation 18B satisfies the predetermined condition; and an errorcorrection using FEC is unable to be made to the communication data, thedetermination part 14C may determine that a burst loss has occurred.

If the determination part 14C determines that no burst loss has occurred(No at Step S114), this routine is ended. If the determination part 14Cdetermines that a burst loss has occurred (Yes at Step S114), theroutine continues to Step S116.

At Step S116, the generation part 14D generates a control command signal(Step S116). At this time, the generation part 14D refers to theconnection management information 18C and identifies the node ID of thecommunication destination to which the communication control signal istransmitted. The generation part 14D then notifies the communicationcontrol part 14A of the communication control signal and the node ID ofthe communication destination.

The communication control part 14A controls the communication unit 16 soas to transmit the control command signal generated at Step S116 to eachof one or more of the communication devices 10 identified by theidentification information received from the generation part 14D byperforming a multi-hop wireless communication (Step S118).

Subsequently, the acquisition part 14E acquires the control commandsignal generated at Step S116, from the generation part 14D through thecommunication control part 14A (Step S120).

Subsequently, the change part 14F changes the communication parameter18A to reduce the volume of traffic per unit time in accordance with thecontrol command signal acquired at Step S120 (Step S122).

The communication control part 14A then reads the changed communicationparameter 18A from the storage unit 18 (Step S124). The communicationcontrol part 14A controls the communication unit 16 so as to perform amulti-hop wireless communication of the communication data that has beendetermined at Step S106 to have a communication error, with the volumeof traffic according to the communication parameter 18A read at StepS124. Thus, the communication unit 16 transmits again, to anothercommunication device 10, the communication data determined last time tohave a communication error, with the volume of traffic according to thecommunication parameter 18A, after the change (Step S126). This routineis then ended. After processing at Step S126, the routine may return toStep S106 described above.

Meanwhile, if the determination is negative at Step S100 (No at StepS100), the routine continues to Step S128. At Step S128, thecommunication control part 14A determines whether the control commandsignal has been received from another communication device 10 throughthe communication unit 16 (Step S128). If the determination is negativeat Step S128 (No at Step S128), this routine is ended.

If the determination is affirmative at Step S128 (Yes at Step S128), theroutine continues to Step S130. At Step S130, the acquisition part 14Ereceives the control command signal from another communication device 10through the communication control part 14A and the communication unit 16(Step S130).

The change part 14F changes the communication parameter 18A to reducethe volume of traffic per unit time in accordance with the controlcommand signal acquired at Step S130 (Step S132). This routine is thenended.

As described above, the communication devices 10 of the presentembodiment each has the acquisition part 14E and the communicationcontrol part 14A. The acquisition part 14E acquires a control commandsignal regarding the volume of traffic per unit time. The change part14F changes a communication parameter for communication control toreduce the volume of traffic per unit time in accordance with thecontrol command signal. The communication control part 14A performsmulti-hop wireless communications with the volume of traffic accordingto the changed communication parameter.

Here, conventional technologies have had difficulty in preventingcongestion of communication data communicated over a multi-hop network.A conventional technology discloses a technique of recovering a burstloss by a specified time by transmitting an error correcting packetlater than video data by the specified time. With the conventionaltechnology applied to a multi-hop network, however, it has beendifficult to prevent congestion of communication data. Specifically, inthe conventional technology, in which wireless relays are performedmultiple times over a communication path and MAC is not retransmitted inmulticast, more packet losses have occurred on a random basis, therebycausing a disturbance of communication data to occur. Also, with theconventional technology applied to a multi-hop network, data iscontinuously transmitted from a child node while data received from thechild node is transferred to a parent node, which has made it difficultto prevent congestion of communication data.

By contrast, in the communication device 10 of the present embodiment,when the acquisition part 14E acquires the control command signal, thechange part 14F changes a communication parameter to reduce the volumeof traffic per unit time. Thus, in a case in which the control commandsignal is acquired, the communication control part 14A can performmulti-hop wireless communications with other communication devices 10with the volume of traffic according to the communication parameterchanged to reduce the volume of traffic per unit time.

Consequently, communications of packets included in communication datacommunicated over the multi-hop network and packet losses can beprevented in the communication device 10 of the present embodiment.

Congestion of communication data communicated over the multi-hop networkcan, therefore, be prevented in the communication device 10 of thepresent embodiment.

Packet delays can also be prevented in the communication device 10 ofthe present embodiment. Thus, the end that receives communication datafrom the communication device 10 of the present embodiment can receivecommunication data in which a disturbance and missing are prevented. Inother words, in addition to the aforementioned effects, thecommunication device 10 of the present embodiment can prevent adisturbance and missing from occurring in video data, which is anexample of communication data.

Packet losses can also be prevented in the communication device 10 ofthe present embodiment. Thus, the end that receives communication datafrom the communication device 10 of the present embodiment can receivecommunication data in which a disturbance is prevented. In other words,in addition to the aforementioned effects, the communication device 10of the present embodiment can prevent a disturbance from occurring invideo data, which is an example of communication data.

In the present embodiment, the case in which the network topology of themulti-hop network that constitutes the communication system 1 has beenillustrated as an example (see FIG. 1). The network topology of thecommunication system 1, however, is not limited to a tree-shapedtopology. For example, the network topology of the communication system1 may be of star type or mesh type.

In the present embodiment, the case in which the communication devices10 that constitute the communication system 1 each includes thecommunication control part 14A, the detection part 14B, thedetermination part 14C, the generation part 14D, the acquisition part14E, and the change part 14F has been described as an example. However,at least one of the communication devices 10 that constitute thecommunication system 1 may include the communication control part 14A,the detection part 14B, the determination part 14C, the generation part14D, the acquisition part 14E, and the change part 14F.

The computer programs to execute the aforementioned processing in theembodiment described above may be configured to be provided by beingrecorded into a computer-readable recording medium, such as a CD-ROM,FD, CD-R, DVD, USB memory, in a installable or executable file format,or may be configured to be provided or distributed via a network such asthe Internet. Various types of computer programs may also be configuredto be provided by being preinstalled on a ROM or the like.

The computer programs to execute the aforementioned processing in theembodiment described above have a modular configuration including theaforementioned functional parts. As actual hardware, for example, a CPU(processor circuit) reads the aforementioned computer program from a ROMor an HDD and executes the computer program, whereby the functionalparts are loaded into a RAM (main memory) and the functional parts aregenerated into the RAM (main memory). The functional parts can also beimplemented in whole or in part using special-purpose hardware, such asan application specific integrated circuit (ASIC) and afield-programmable gate array (FPGA).

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An electronic apparatus comprising: processingcircuitry configured to: determine whether a burst loss of transmissiondata transmitted from the electronic apparatus by a multi-hop wirelesscommunication has occurred, the burst loss being determined based on adetected packet loss of the transmission data; in response todetermining that the burst loss has occurred, generate a first controlcommand instructing electronic apparatuses including the electronicapparatus to reduce a transmission rate representing a volume of trafficper unit time; and change a communication parameter to reduce atransmission rate applied to the electronic apparatus in accordance withthe first control command; and communication circuitry configured to:output the first control command generated by the processing circuitryto a communication path of the multi-hop wireless communication suchthat the first control command is transmitted to one or more of theelectronic apparatuses that are connected in a direction toward acommunication destination of the transmission data corresponding to thedetected packet loss; and transmit again the transmission data byperforming a multi-hop wireless communication with a transmission rateaccording to the changed communication parameter.
 2. The electronicapparatus according to claim 1, wherein the communication circuitry isconfigured to receive a second control command to reduce thetransmission rate, the second control command being sent from anotherelectronic apparatus over a communication path of the multi-hop wirelesscommunication, and the processing circuitry is configured to change thecommunication parameter to reduce the transmission rate applied to theelectronic apparatus in accordance with the second control command. 3.The electronic apparatus according to claim 1, wherein the communicationparameter includes at least one of a bit rate of transmission data and aframe rate of the transmission data.
 4. The electronic apparatusaccording to claim 3, wherein the communication parameter includes atleast one of a bit rate of transmission data and a frame rate of thetransmission data, and a forward error correction parameter.
 5. Acommunication method implemented by a computer installed in one ofelectric apparatuses, the method comprising: determining whether a burstloss of transmission data transmitted from the computer by a multi-hopwireless communication has occurred, the burst loss being determinedbased on a detected packet loss of the transmission data; in response todetermining that the burst loss has occurred, generating a first controlcommand instructing the electric apparatuses to reduce a transmissionrate representing a volume of traffic per unit time; changing acommunication parameter to reduce a transmission rate applied to thecomputer in accordance with the first control command; outputting thegenerated first control command to a communication path of the multi-hopwireless communication such that the first control command istransmitted to one or more of the electric apparatuses that areconnected in a direction toward a communication destination of thetransmission data corresponding to the detected packet loss; andtransmitting again the transmission data by performing a multi-hopwireless communication with a transmission rate according to the changedcommunication parameter.
 6. The communication method according to claim5, further comprising: receiving a second control command to reduce thetransmission rate, the second control command being sent from anothercomputer over a communication path of the multi-hop wirelesscommunication; and changing the communication parameter to reduce thetransmission rate applied to the computer in accordance with the secondcontrol command.
 7. A computer program product having a non-transitorycomputer readable recording device in which executable instructions arestored, wherein the instructions, when executed by a computer installedin one of electric apparatuses, cause the computer to perform:determining whether a burst loss of transmission data transmitted fromthe computer by a multi-hop wireless communication has occurred, theburst loss being determined based on a detected packet loss of thetransmission data; in response to determining that the burst loss hasoccurred, generating a first control command instructing the electricapparatuses to reduce a transmission rate representing a volume oftraffic per unit time; changing a communication parameter to reduce atransmission rate applied to the computer in accordance with the firstcontrol command; outputting the generated first control command to acommunication path of the multi-hop wireless communication such that thefirst control command is transmitted to one or more of the electricapparatuses that are connected in a direction toward a communicationdestination of the transmission data corresponding to the detectedpacket loss; and transmitting again the transmission data by performinga multi-hop wireless communication with a transmission rate according tothe changed communication parameter.
 8. The computer program productaccording to claim 7, wherein the instructions further cause thecomputer to perform: receiving a second control command to reduce thetransmission rate, the second control command being sent from anothercomputer over a communication path of the multi-hop wirelesscommunication; and changing the communication parameter to reduce thetransmission rate applied to the computer in accordance with the secondcontrol command.
 9. A communication system comprising: a plurality ofelectronic apparatuses configured to perform a multi-hop wirelesscommunication, wherein at least one of the electronic apparatusescomprises: processing circuitry configured to: determine whether a burstloss of transmission data transmitted from the electronic apparatus by amulti-hop wireless communication has occurred, the burst loss beingdetermined based on a detected packet loss of the transmission data; inresponse to determining that the burst loss has occurred, generate afirst control command instructing the plurality of electronicapparatuses to reduce a transmission rate representing a volume oftraffic per unit time; and change a communication parameter to reduce atransmission rate applied to the at least one of the electronicapparatus in accordance with the first control command; andcommunication circuitry configured to: output the first control commandgenerated by the processing circuitry to a communication path of themulti-hop wireless communication such that the first control command istransmitted to one or more of the plurality of electronic apparatusesthat are connected in a direction toward a communication destination ofthe transmission data corresponding to the detected packet loss; andtransmit again the transmission data by performing a multi-hop wirelesscommunication with a transmission rate according to the changedcommunication parameter.
 10. The communication system according to claim9, wherein the communication circuitry is configured to receive a secondcontrol command to reduce the transmission rate, the second controlcommand being sent from another electronic apparatus over acommunication path of the multi-hop wireless communication, and theprocessing circuitry is configured to change the communication parameterto reduce the transmission rate applied to the electronic apparatus inaccordance with the second control command.